1 files changed, 12 insertions, 0 deletions

diff --git a/include/linux/sched.h b/include/linux/sched.h
index a4ab9daa387c..b7b9501b41af 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -762,6 +762,18 @@ struct signal_struct {
         unsigned audit_tty_log_passwd;
         struct tty_audit_buf *tty_audit_buf;
 #endif
+#ifdef CONFIG_CGROUPS
+        /*
+         * group_rwsem prevents new tasks from entering the threadgroup and
+         * member tasks from exiting,a more specifically, setting of
+         * PF_EXITING.  fork and exit paths are protected with this rwsem
+         * using threadgroup_change_begin/end().  Users which require
+         * threadgroup to remain stable should use threadgroup_[un]lock()
+         * which also takes care of exec path.  Currently, cgroup is the
+         * only user.
+         */
+        struct rw_semaphore group_rwsem;
+#endif
 
         oom_flags_t oom_flags;
         short oom_score_adj;            /* OOM kill score adjustment */